AV (Audio and Visual) preamplifiers, for example, in which audio signals have been digitized, use a processing circuit such as a DSP to perform signal processing such as decoding, effecting, and equalizing. When the DSP is used, a program executed by the DSP can be modified to change the content to be processed.
Therefore, there has been conceived an AV preamplifier which is provided with a non-volatile, rewritable memory in which a program executed by the DSP is stored. This allows the program stored in the non-volatile memory to be rewritten to update functionality of the AV amplifier or add a new function, so that the functionality of the AV amplifier can be up-to-date at any time.
For example, when a novel encoding method is used for a digital audio signal, the corresponding decoding method can be added to the AV amplifier, or, when new effecting is put into practice, the effecting can be added to the AV amplifier. Furthermore, a program executed by the DSP can be improved to obtain a higher quality audio signal, or a bug can be removed from a bugged program. Thus, the AV amplifier can be upgraded to an up-to-date one.
A flash memory has been used in general as the above-noted non-volatile, rewritable memory. In order to rewrite a program stored in the flash memory, it is necessary to erase the program in the flash memory before rewriting.
If a new function is added while an old function remains, the overall content of the flash memory must be rewritten, and it is therefore necessary to install versions in order, such as Ver. 1→Ver. 2→Ver. 3, in order to update the functionality. Thus, it is impossible to select and install only a function that is newly added in Ver. 3 to update the functionality.
In addition, functions newly added by versions are of different value from one version to another. As a result, for example, even if a function that is added in Ver. 3 is of less value than a function that is added in Ver. 2, it is necessary to set the price of Ver. 3 to a higher price than that of Ver. 2 although Ver. 3 must have been offered at a lower price.
The present invention is intended to solve such problems.